The Met Office has issued yellow and amber weather warnings across Wales which could cause heavy rainfall and disruption.
Some parts of the country could have more than 100mm of rain in the next 24 hours.
A yellow 'be aware' weather warning is currently in force across most of Wales and will expire at 2am on Sunday.
The heavy rainfall forecast could result in homes and businesses being flooded, causing damage to some buildings.
Surface water on the roads could also cause some difficult drivings conditions, with train and bus services likely to be affected by the wet weather.
The amber weather warning covers most of south Wales and will be in force from 8pm on Friday to 6pm on Saturday.
The Met Office says spray and flooding could lead to difficult driving conditions and some road closures, with a 'good chance' some communities may be cut off by flooded roads.
There is also a risk of powers cuts and a loss of other services to some homes and businesses.
It was Wales' third major flooding event in the last 11 months.
The devastating flooding in Skewen in January, caused by water from old mine workings, meant many people will not be able to return to their homes for months to come.
The flood is thought to have been caused by an underground drainage route that became blocked. Over time, water backed up and filled a disused shaft under a road in the village.